Contact fastener connections are used in many areas to fasten objects or components such that they can be detached again. In motor vehicles, to prevent the mats from slipping or lifting up, the mats are frequently secured to the vehicle floor in such a way that connecting parts, which are anchored to the floor, and which have adhesive and/or hooking elements, are brought into adhesive contact or interlocking engagement with attachment parts fastened to the floor mats, and having corresponding adhesive and/or hooking elements. In the prior art, the connecting parts are designed having a disk-shaped support part, which can be anchored to the vehicle floor. On the upper side of the support part, a fastening part having adhesive and/or hooking elements is attached. This attaching is done by chemical or thermal adhesive bonds, for example using adhesives or hot glues that contain solvents. Apart from the environmental impact associated with solvent-containing substances, neither the chemical, nor the thermal adhesive bonds are satisfactory. As has been shown, when used in floor mats in motor vehicles, a risk exists that the fastening part and the support part will become detached from one another when the temperature and/or the relative humidity in the vehicle is too high. Another risk is detachment when the floor mat has been used for an extended period of time. This detachment constitutes a safety risk, in particular, when the floor mat on the driver's side slides forward towards the pedals while driving. That sliding can lead to uncertainty on the part of the driver and may possibly result in an accident.
To avoid the risk that the fastening part may become detached from the support part, a solution disclosed in DE 10 2009 054 896 A1 is also prior art. According to that solution, the connecting part is produced such that the support part and hooks are simultaneously formed as fastening elements in a single process step in an injection mold. Although in this procedure, there is practically no risk of detachment, the number of hooks that can be formed in the injection mold in which the support part is molded is nevertheless extremely limited, for example to a number not exceeding 50 hooks per cm2. Such a limited achievable packing density of the hooking elements is not satisfactory.
To retain the advantage of the integrated design of the support part and fastening part in a connecting part, while at the same time avoiding the disadvantages of an inadequate design of the fastening part, according to a teaching disclosed in the patent application, DE 10 2013 009 091 A1, the fastening part, with the adhesive and/or hooking elements thereof, is produced in a first step, and introduced as an insert part into an injection mold. In that mold, the connecting part in the form of a component is formed in a second step by a back injection process. The connecting part then contains the fastening part as an integrated component. A connecting part can thereby be produced, for which there is no risk of detachment due to the integrated formation of support part and fastening part, and in which the adhesive and/or hooking elements can be designed in different ways because the fastening part can be prefabricated as an insert part in a separate production process. Hooks, loops or mushroom-shaped elements having round or flat heads may also be provided and can be produced having very high packing densities using special processes provided to this end. In carrying out this method, during the back injection process, in which a molten mass made of a thermoplastic synthetic material such as polyamide or polypropylene, preferably having glass fiber reinforcement, is injected into the injection mold, the method must ensure that no damage occurs to the elements of the fastening part as a result of excessive molding pressure, such as the flattening of the adhesive or hooking elements. To eliminate this risk, a correspondingly complex design of the injection mold is necessary, for example, to avoid longer flow paths and the increased injection pressures that such a flow path requires.